Corals, our ANIMAL friends!

When people think of corals, they usually think plant… However, corals are in fact, marine animals... and carnivorous ones at that!

There are thought to be around 6,000 species of coral around the world and just under 300 species in Nusa Penida alone! Corals not only provide us divers with a stunning vista on our dives but more importantly, they support marine life by providing homes and shelter to coral reef residents and protect the coastline. They come in a hugely diverse range of shapes and colours and have complex symbiotic relationships.

The basics

Coals are marine invertebrates, classified under the Kingdom; Animal and the Phylum; Cnidaria.  There are many different types and species of corals notably, hard and soft.  

Hard corals have an external skeleton made of calcium carbonate, whereas soft corals lack this external skeleton and instead, have internal structures called sclerites, which confusingly, are also made of calcium carbonate!

The sum of its parts

‘Coral’ is a collective term; each coral is made up of thousands, maybe hundreds of thousands of ‘polyps’.

A polyp is an animal; an invertebrate with both stinging tentacles and stomachs. Passing organic marine matter, such as algae and zooplankton, are caught with their tentacles and fed into the opening leading to their stomach. 

Polyps have a symbiotic relationship with a tiny plants called zooxanthellae.  Corals provide the Zooxanthellae with an environment, which facilitates photosynthesis. The products produced by the zooxanthellae during photosynthesis, in turn, provide the corals its vital nutrients.  These include, calcium carbonate, which the polyp uses to create its skeleton. 

Using this skeleton, the coral polyp attaches itself to rocks or the sea floor, where they begin to multiply using an asexual reproduction method called ‘budding’.  A group of genetically identical polyps is called a ‘colony’. What starts as a tiny polyp about a millimeter long, can grow to form immense colonies weighing several tons.  Many colonies grow to form coral reefs, which can be so enormous – like the great barrier reef, which can be seen from space!

Coral Reefs

Coral reefs are the foundation of the ocean, supporting other marine life with both food and shelter.  Some marine life feed on the corals and, a quarter of all marine species use coral reefs as a home. Coral reefs also act as protection for the coast line by providing a natural barrier which can reduce wave energy thus reducing erosion and protection from storms.

Corals come in such a wide variety, and here a few we can see in Nusa Penida:-

HARD CORALS

Acropora Corals

These are easy to recognise branching corals with species including:  Staghorn, Elkhorn and Table coral.

Porites

These corals are more hemispherical with a smooth surface.  Species include lobata, solida and lutea

Lobophillia

Another type of hard corals known as ‘brain corals’.  Species include, Echinophyllia, hemprichii, serata and recta.

SOFT CORALS

Fungiidae corals 

These are typically flat or dome-shaped and can resemble mushrooms, examples of these corals include, mushroom coral, heliofungia, Pleuractis and Ctenactis

Xenia Corals

Recognised by their arms, which open and close to collect food, species include: pulsing xenia and pom-pom xenia